The present invention relates generally to scaffold bracket assemblies and more particularly, to load activated locks for scaffold bracket assemblies.
Angle brackets and bracket assemblies are well known in the art.
Angle brackets typically comprise three main structural components, a horizontal leg, a diagonal leg and a vertical leg, which are configured to define, in load-bearing shape, a substantially triangular bracket. In the art, angle brackets typically fall into two categories, one-piece angle brackets and multiple-piece angle brackets.
In U.S. Pat. No. 5,257,766 to Riblet, there is disclosed an angle bracket constructed from a single piece metal bracket. The bracket is of a substantially triangular shape. In one embodiment of the invention, the bracket has a U-shaped cross-section providing added stability. A method is disclosed for constructing the bracket from the metal blank. The method includes the steps of folding the metal blank along preformed fold sections to form its triangular shape. The method also includes the steps of folding the metal blank along additional preformed fold lines to form its U-shaped cross-section.
Bracket assemblies typically comprise an angle bracket of the type described above, an upper bracket arm and a lower bracket arm. The upper bracket arm and the lower bracket arm are sized and shaped to be mounted on a vertical upright. In use, each of a pair of bracket assemblies is commonly mounted onto an associated upright, such as a post or beam, to create a scaffold. A scaffold is created by placing a horizontal plank across the angle bracket of each bracket assembly.
One type of bracket assembly which is well known and widely used in the art is disclosed in U.S. Pat. No. 2,342,427 to Riblet. The bracket assembly comprises a horizontal leg, a diagonal leg and a vertical leg which are configured to define, in load-bearing shape, a substantially triangular angle bracket. The bracket assembly further comprises an automatic lock which is affixed to the angle bracket at the junction of the vertical leg and the horizontal leg and a lower bracket arm which is affixed to the angle bracket at the junction of the vertical leg and the diagonal leg.
The automatic lock of the bracket assembly comprises a U-shaped band which is pivotally mounted onto the angle bracket about a fulcrum. The automatic lock of the bracket assembly further comprises a cylindrically shaped inner jaw and a cylindrically shaped outer jaw, the inner jaw being disposed beneath the plane defined by the fulcrum and the outer jaw.
The bracket assembly can be mounted on an upright by slidably disposing the bracket assembly so that the upright projects between the inner jaw and the outer jaw. When a load is placed on the horizontal leg of the angle bracket, the resulting force pivots the lock about the fulcrum in a counterclockwise direction until the inner and outer jaws abut against the upright in such a manner so as to prevent any downward movement of the bracket assembly along the upright.
Bracket assemblies of this type are highly desirable because the force of the inner jaw and the outer jaw onto the upright is provided entirely by the load on the platform. Specifically, the load creates a frictional force between the outer jaw and the upright which precludes the bracket assembly from sliding down the upright.
Although widely used in commerce, bracket assemblies of this type experience a notable drawback. In particular, it has been found that bracket assemblies of this type function inadequately when mounted on an upright of reduced thickness. Specifically, when a bracket assembly of this type is mounted on an upright of reduced thickness, a considerable amount of rotation of the lock about the fulcrum is required in order for the inner and outer jaws to properly abut against the upright to limit downward movement of the bracket assembly along the upright. Accordingly, it has been found that when the lock is required to rotate so that the outer jaw is disposed above the horizontal plane defined by the horizontal leg and the fulcrum, the outer jaw inadequately engages the upright. As a consequence, the bracket assembly may slide down the upright, which is highly undesirable.